Google said Tuesday it will follow the activities of users across e-mail, search, YouTube and other services, a shift in strategy that is expected to invite greater scrutiny of its privacy and competitive practices.

The information will enable Google to develop a fuller picture of how people use its growing empire of Web sites. Consumers will have no choice but to accept the changes.

The policy will take effect March 1 and will also impact Android mobile phone users, who are required to log in to Google accounts when they activate their phones.